add check if no removable files to don't throw null error

Tools/tidy_files_for_release.ps1

@@ -7,15 +7,15 @@ param (
     [Parameter(Mandatory=$true)]
     $ConfigurationName
 )
-
+Write-Output ""
 Write-Output "===== Beginning $($PSCmdlet.MyInvocation.MyCommand) ====="
 
 # Remove unnecessary files from Release versions
-if ($ConfigurationName -match "Release") {
-    Write-Output "Removing unnecessary files from Release versions"
-
+if ($ConfigurationName -match "Release") 
+{
     $test = Join-Path -Path $TargetDir -ChildPath "app.publish"
-    if (Test-Path  $test -PathType Container) {
+    if (Test-Path  $test -PathType Container) 
+	{
         Remove-Item -Path (Join-Path -Path $TargetDir -ChildPath "app.publish") -Recurse -Force
     }
 
@@ -29,10 +29,18 @@ if ($ConfigurationName -match "Release") {
     ) -Exclude @(
         "mRemoteNG.VisualElementsManifest.xml"
 	)
-    Remove-Item -Path $filesToDelete.FullName
-    Write-Output $filesToDelete.FullName
+	if ($filesToDelete) 
+	{ 
+		Write-Output "Unnecessary files are detected and will be removed" 
+		Remove-Item -Path $filesToDelete.FullName
+		Write-Output $filesToDelete.FullName
+	} else 
+	{
+		Write-Output "  No unnecessary files are detected"
+	}
 }
-else {
+else 
+{
     Write-Output "We will not remove anything - this is not a release build."
 }